Electrodynamic sound-reproducing system



Oct. 29, 1929. B. F. MlEssNER 1,733,232 v ELECTRODYNAMIC SOUNDREPRODUCING SYSTEH I Filed )lax-ch 6, 1929 wwf/MM f 3% www Patented Oct.29, T1929.. y i 1 UNITED'STATES PATENT OFFICE BENJAMIN' F. MIESSNER, 0FSHORT HILLS, NEW JERSEY if ELECTRODYNAMIC SOUND-REPRDUCING SYSTEMApplication filed March 6, 1929. Serial No. 844,883.

The present invention relates to sound reor an electrolytic rectifier,both kinds being producing systems, and particularly to such so used.systems employing signal reproducing de- The armture coil A is shownenergized by vices requiring energizing for operation, such the signalcurrents to be reproduced as sound as the so-called electrodynamic typeof re- .through a transformer T2, which may be for; producer. instancethe output element of a cascaded am- Anobject of the invention is t0energize a plifier system. The signal currents flowing reproducerrequiring a strong magnetic field through coil A react on the fieldproduced by from a readily available source of unsteady coil to producemotion of coil A and atcurrent, such as rectified alternating currenttached cone C in accordance with the sound 60 of a commerciallyavailable 60 cycle source, representing signal currents. However, thewithout encountering an annoying degree of rectified field energizingcurrent through coil, hum, F is not steady, thus producing an unsteady Afurther object is to employ the current of field tending to produce humreproducing a filter system associated with an alternating motion ofcoil A. This I oppose by introe5 current rectifier as a source forenergizing a ducing a selected amount of current of the system of vacuumtube amplifiers in the adsame character as that in field coil F intoarditional function of energizing the reproducer A mature coil A by wayof coupling resistance associated with the system, while keeping R, theamount of current being selected in,

hum effects adequately small to be non-disany desired Way, as by a tap Son resistance I0` turbing. R, which tap may be permanently setonc'etheThe invention is readily understood from desired adjustment is found.The connecthe following description with the aid of the tion of the coilA to the resistance R is so figures of the accompanying drawing in poledthat the effect of the fiuctuating current which like referencecharacters represent like in Coil A opposes the effect of thefluctuating 75 parts so far as possible in the several figures. currentin coil F.

Fig. 1 is an illustration in diagram of an The device of course can beusedwin fashion electrodynamic form of sound reproducer reverse to thatof Sound reproduction; that iS., connected to employ my invention. as asound pick-up or microphone, in which Fig, 2 illustrates 9, modification0f the 3,1'- CaSe Creating SOllnd in the Vicinity 0f C0116 C 80rangement 0f Fig- 1. sets the coil A in motion to generate sound Fig. 3diagrammatically illustrates an elecrepresenting currents which maybepassed to trodynamicreproducer associated with a filan amplifier orother device through transter system in a manner to employ features offormer T2.

x5 my invention. In Fig. 2 I show a transformer T3 substi- 85 Fig. 4illustrates a modication of the artuted for the resistance R of Fig. 'lfor transrangement of Fig. 3. ferring the hum-bucking energy to coil A`in Referring to' Fig. l, the usual electrothis Way avoiding introducingany of the didynamic reproducer is shown as having a rect currentcomponent into the coil A circuit.

40 magnetic core M on which is wound an ener- Of course anauto-transformer, or any other 90 gizing or field producing coil F. Amovable suitable form of coupling between the two or armature coil A isshown associated with circuits may be used. Other than this couthe fieldof the core M, and having attached pling, Fig. 2 is the same as Fig. 1.thereto a cone or other suitable sound gen- In Fig. 3 I show the fieldcoil F of the reerator. v producer used as the choke coil of a filtersys- 95 The field coil F is shown energized from antem of generalcharacter, shown to have filter alternating current source through asuitable condensers C, and C2. The filter is shown fed transformer T1 byWay of a rectifier D, which from the usual rectifier system having arecmay be either a full wave or single wave rectifier tube D energizedthrough secondarie tifier of'suitable kind, such as a tube rectifier `S,and S2 cfa transformer T1 connected into 100 an alternating currentsupply system. The filter system 1s shown to supply a load E,conventionally shown, which may be for eX- ample the plate circuits of acascaded series of vacuum tubes.

As before the reproducer is shown to have a movable coil A associatedwith a reproducing cone C. Input of sound representing current to coil Ais by way of transformer T2, which may be for instance the output of anamplifier system the plate circuits of the tubes of which form the loadE on the filter system.

I show a resistance R, coupling the movable coil circuit with the filtercircuit, so that some of the same character of current that flowsthrough coil F is introduced into coil A for hum neutralizing asdescribed in connection with Fig. 1, it being understood that thecircuits may be coupled by a transformer as in Fig. 2, or through othersuitable form of coupling. In Fig. 3 the field coil F serves theadditional useful function of acting as a filter choke. thereby savingfrom the system the weight and cost of such an element.

In Fig. 4 I show for example the output tube VT of a cascaded amplifiersystem connected to the same supply and filter system of Fig. 3 forenergizing the plate circuit thereof, the input circuit being shown toinclude as a sound representing current input element a transformer Twhich may be the output of a series of cascaded nt-ubes also energizedby the filter system.

The energizing of the filament and grid electrodes of tube VT is shownin accordance with standard practice. and requires no detaileddescription, not being a feature of the present invention.

In this Figure 4 arrangement I sh ony the armature coilAof thereproducerenergizedivith sound representing currents from the output of tube VTthrough transformer Tg. For hum bucking I provide a coil B associatedwith core M to pickup some of the fluctuations due to unsteady currentthrough field coil F. and introduce these hum bucking currents intoarmature coil A by way of the grid circuit of tube VT, and thus, afteramplification, into transformer T2 to coil A. and of course can poleeither transformer T2 or coil B to get the desired neutralizing phase. Ishow coil B to have a tapped connection S, but this may be determinedand permanently fixed by the design of the coil in a given design.

The adaptation of the features of my invention to various like systemswill be apparent to those practiced in the art from the descriptionIhave given. and I intend no limitations by reason of having confined mydescription to a limited number of typical examples of its employment,the scope of tue invention being set forth in the accompanying claims.

Having thus described my invention, what I claim is:

1. In a device for translating electrical signal energy into soundenergy, the combination of a source of alternating current energy, arectifier for convertingsaid alternating current into unidirectionalcurrent having a ripple component, a coil connected between theelectrodes of said rectifier whereby a strong magnetic field of constantpolarity is developed around said coil, a conductive element mounted forvibrational movement within said field, means for passing signalcurrents through said conductive element whereby said conductive elementis vibrated at the signal current frequency, and means for transferringa. regulable portion of said ripple component of the unidirectionalcurrent from said source to said conductive element, of a phase tosubstantially eliminate vibrationof said conductive member by thelvariation in field intensity caused by the ripple component of saidunidirectional current.

2. In a device. for translating electrical signal energy into soundenergy, the combination of a source of alternating current energy, arectifier for converting said alternating current into unidirectionalcurrent having a ripple component, a coil connected between theelectrodes of said rectifier whereby a strong magnetic field of constantpolarity is developed around said coil, a conductive element mounted forvibrational movement within said field, means for passing signalcurrents through said conductive element whereby said conductive elementis vibrated at the signal current frequency, means for diverting aregulable portion of said ripple component of said unidirectionalcurrent from said coil, and means for introducing this diverted portioninto said conductive element of a phase to substantially eliminatevibration of said conductive member by the variation in field intensitycausedby the ripple component of said unidirectional current.

3. In a device for translating electrical signal energy into soundenergy the combination of a source of. alternating current energy, arectifier for converting said alternating current into unidirectionalcurrent having a ripplekcomponent, a coil connected between theelectrodes of said rectifier whereby a strong magnetic field of constantpolarity is developed around said coil, a conductive element mounted forvibrational movement within said field. means for passing signalcurrents through said conductive element whereby said conductive elementis vibrated at the signal current frequency, a second coil coupled tothe coil-rectifier circuit for diverting a regulable portion of theripple component of said unidirectional current therefrom, and means forintroducing this diverted portion into said conductive element of aphase to substantially eliminate vibration of said conductive member bythe variation in field intensity caused b the ripple component of saidunidirectiona current.

4. In a device for translating electrical signal energy into soundenergy the combination of a source of alternating current en ergy, arectifier for converting said alternating current into unidirectionalcurrent having a ripple component, a coil connected between theelectrodes of said rectifier whereby a strong magnetic field vofconstant polarity is developed around said coil, a conductive elementmounted for vibrational movement Within said field, means for passingsignal currents through said conductive element Iwhereby said conductiveelement is vibrated f at the signal current frequency, a second coilcoupled to the coil-rectifier circuit for diverting a regulable ortionof the ripple component of said unidirectional current therefrom, athird coil conductively coupled to said element and associated with saidsecond coil for introducing this diverted portion into said conductiveelement of a phase to substantially eliminate vibration of saidconductive member by the variation in field intensity caused by theripple component of said unidirectional current.

5. In a device for translating electrical signal energy into soundenergyr the combination of a source of alternating current energy, arectifier for converting said alternat- A ing current intounidirectional current having a ripple component, a coil connectedbetween the electrodes of said rectifier wherebv a strong magnetic fieldof constant polarity is developed around said coil, a conductive elementmounted for vibrational movement A within saidfield, means for passingsignal currents through vsaid conductive Velement whereby saidconductive element is vibrated at the signal current frequency, a secondcoil coupled to the 'coilrectifier circuit for diverting therefrom aregulable portion of the ripple component of said unidirectionalcurrent, a vacuum tube having a grid, filament and plate, said secondcoil being connected to said grid, a transformer, the rimary of whichconnects said plate to said) coil-recti fier circuit, the secondary ofsaid transformer being associated with said conductive element of aphase to substantially eliminate vibration of said conductive member bythe variation in field intensity caused by the ripple, component of saidunidirectional current.

In witness whereof, I have hereunto subscribed my name this first day ofMarch,

BENJAMIN F. MIESSNER.

